Automotive body panels are typically constructed from a number of separately stamped metal sheets. For example, vehicle doors may include a stamped outer panel fixed to a stamped inner panel to define a door shell. At least one known door shell includes an outer panel spot welded to an inner panel at a number of locations along the outer periphery of the assembly. A spot welding process typically occurs in a dedicated work cell performing only inner panel to outer panel spot welding. Subsequently, the door shell is transferred to one or more stations where fasteners are attached to the inner panel. Conversely, the inner panel may be first transferred to a station where fasteners are coupled to the inner panel and then the inner panel including the fasteners is moved to the welding station for interconnection with the outer panel as previously described.
The requirement for multiple workstations and multiple sets of tooling greatly increases the cost and time required to manufacture a vehicle component. Depending on the method used to attach the fasteners, difficulties may arise in providing access to the tooling to assure proper fastener mounting. For example, a tubular member may require machining to provide apertures allowing access for electrodes on one side of a resistance welded joint. The additional machining and mechanical strength degradation may be undesirable.
Furthermore, other fasteners may require relatively large amounts of energy over an extended period of time to provide a desired joint strength. One example includes attempting to laser weld nuts having relatively large thicknesses equal to the length of a threaded aperture of the fastener. The time and energy required to couple the thick fastener may be prohibitive.
Attempts to couple mechanical fasteners to sheet steel via a laser welding process have been challenging. To prevent corrosion of the fastener and/or the substrate, a galvanized coating is often used. One known welding attempt includes providing a fastener having a substantially smooth planar surface abutting a substantially smooth planar surface of a galvanized substrate. During the laser welding process, the galvanized coating boils and zinc gas is emitted. The zinc gas is temporarily trapped between the substantially smooth planar surfaces of the fastener and the substrate until sufficient energy is gained for the gas to escape. Parent material of the substrate and/or the fastener may be ejected based on the pressure and energy provided from the zinc gas. After the parent material is ejected, undesirable porosity or holes are formed requiring the assembly to be scrapped or reworked. If ejection of the parent material does not occur, the weld may be otherwise negatively affected due to the presence of the zinc gas. Accordingly, a need exists in the art to provide improved laser welding methods and laser welded products.